Trading off food and risk: do elk in cutblocks modify residency time or visitation rate?
Visscher, Darcy *,1, Merrill, Evelyn1, Beyer, Hawthorne1, Frair, Jacqueline1, 1 University of Alberta, Edmonton, Alberta, Canada
ABSTRACT- We used elk movement models to investigate the relative importance of forage availability, predation risk and human disturbances in and adjacent to cutblocks to influence the time elk spend in cutblocks in the east slope of Alberta. We used random correlated walk (CRW) models to derive the time elk would be expected to spend in cutblocks in their home ranges based only on size and shape, and related the difference in the expected and the observed residency time of GPS collared elk in cutblocks to conditions elk experience along their movement paths. Simulated elk movements were based on observed step lengths and turning angles from 28 resident female elk while in cutblocks during summer (15 June-15 September) in 2001-2003. Forage availability of a cutblock was based on an age to biomass relationship calculated from sampling 159 cutblocks varying in age from 0 to 37 years since harvest. Predation risk was calculated from a summer wolf resource selection function (RSF), which provided a metric for the riskiness of a location based on the relative probability of occurrence for a wolf. Human disturbance was quantified using road density as a surrogate. We found that the total adjusted time elk spent in cutblocks over a month period was a continuum of both time per visit but also the number of visitation events, suggesting that elk tradeoff predation risk and forage availability not only through patch residency duration but also visitation rate. We discuss our results in context of current forestry guidelines for elk in Alberta and make recommendations for their improvement based on both the temporal and spatial arrangement of cutblocks within a heterogeneous landscape.
Key words: forestry, patch residency time, visitation rate
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